CAUTION: Many of these experi-ments require adult supervision, and some should not be performed by children at all.
How to Build a
HovercraFTAmazing DIY Science Projects
STEPHEN VOLTZ AND FRITZ GROBEa.k.a. the Coke and Mentos Guys
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STEPHEN VOLTZ AND
FRITZ GROBEare the founders of EepyBird. In the EepyBird
Laboratory in Maine, they experiment with Coke
and Mentos, sticky notes, paper airplanes, ping
pong balls, and more, searching for ways to
transform these things from everyday life into
something new and unforgettable.
In 2006, they started an Internet phenomenon
with the release of the viral video classic, “The
Extreme Diet Coke and Mentos Experiments.”
Since then, they’ve taken their crazy science
experiments to The Late Show with David
Letterman, Ellen, The Today Show, and
Mythbusters, as well as live events in Las Vegas,
New York, London, Paris, and Istanbul.
EepyBird has received four Webby Awards, two
Emmy nominations, and their videos have now
been seen over 150 million times.
Manufactured in China
When a Love of Science Meets a Love of Awesome, Ordinary Objects become Extraordinary Experiments. Learn to . . .
• Amaze onlookers as your head inflates to twice its size
• Pierce a balloon without popping it
• Power a mini-rocket car with Coke and Mentos
• Blow out a candle 25 feet away with a giant air vortex cannon
• Cause a metal can to crush itself
You’re never too old to be the coolest kid on the block.
Levitation, combustion, magnetism.Science yields some pretty cool stuff. What’s even
cooler is pulling off some of the most awesome science
experiments of all time—in your own home. Using
ordinary, household objects and clear, illustrated
instructions, Stephen Voltz and Fritz Grobe (the brilliant
mad scientists behind the Coke and Mentos geyser
phenomenon) make 25 epic experiment extravaganzas
accessible to cool-stuff connoisseurs of all levels.
Then they add one more thing: science. Each experiment
includes a careful explanation of the science that makes
it work, thoroughly breaking down the principles in a way
that will inspire a love of scientific experimentation and
take you from amateur to genius level in no time. You’ll
construct a paper plane that flies forever, make Coke
and Mentos fountains of Bellagio proportions, and, yes,
build a hovercraft.
And you’ll do it all on your own, eventually gaining
enough expertise to figure out your own variations and
new experiments. With an appetite for really, really cool
stuff, and knowledge of the science behind it, nothing
can stop you from making the world your science lab
and transforming the objects around you into impressive
scientific productions.
Put on your safety goggles and get started.
Air Cannons, Magnet Motors, and 25 Other
How to Build a HovercraFT
Voltz
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$24.95 U.S. / £15.99 U.K.
HOW TO BUILD A HOVERCRAFT 6362 HOW TO BUILD A HOVERCRAFT
[spiderweb.heroshot.tif] Want to magically walk right through a giant spiderweb without it
touching you? This fun trick lets you create a video that shows you
standing behind a web made of tape that stretches across a doorway.
When you walk forward, you appear to melt right through the tape until
you’re suddenly standing in front of the web!
HOW DOES IT WORK?
Two-dimensional images like videos flatten three-
dimensional reality and force our brain to make
some guesses about what we’re looking at. As we saw
with The Face that Follows (page 12), our brain can
misinterpret what it sees. In particular, we guess at
how big objects in a two-dimensional image are, based
on things like how much space they take up in the
image and what context they appear in.
Because of this, our brain can be deceived. Peter
Jackson’s Lord of the Rings movies do this a lot. He films
in a way that tricks us into thinking that all those
adult actors playing hobbits are much smaller than
they actually are. This optical illusion is called forced
perspective.
With the right camera angle and the right alignment
of objects, the enormous Taj Mahal can be made to
appear small enough for someone to simply reach out
and touch the top.
Here, you use the technique of forced perspective to
make an image that looks like a spiderweb stretched
across a doorway. Actually, it’s two separate webs that
only look like one.
08 the spiderweb illusion
HOW TO BUILD A HOVERCRAFT 6564 HOW TO BUILD A HOVERCRAFT
THE EXPERIMENT: THE SPIDERWEB ILLUSION
This illusion requires a doorway with enough space
on one side for the video camera to capture the entire
doorway in the image. For the photos in this book, we
used a double doorway to make the illusion bigger, but
a single doorway will work as well. This project also
requires two people: one person builds the web while
the other looks through the video camera and guides
the web builder.
HOW TO BUILD IT
STEP ONE: Position the camera on the tripod at an
angle to the door and off to the right of the door so that
the entire doorway appears in the image. The photo
shows a good position for the camera. Once you’ve got
the camera in position, don’t move it or adjust the zoom.
It must remain fixed in place from now on.
NOTE: It doesn’t matter on which side of the doorway
you place the camera. However, if you put your camera
to the left of the door, reverse the directions listed
below (that is, left becomes right, and right becomes
left). Further, remember that all the directions we give
below are from the point of view of the camera. So when
we say “left,” we mean left from the perspective of the
person behind the camera looking at the door.
STEP TWO: Start making the masking tape web with
3 pieces: 1 connects from the center of the door frame
straight down to the floor, and 2 connect from the center
of the door frame to the top corners of the door frame,
so that it looks like you’re making a peace sign.
STEP THREE: Now fill in just the right side and the top of
the web, running more strips out from the center of the
web to the door frame and then connecting them with
short strips of tape going around the web.
MATERIALS
■ 1 roll of masking tape (blue painter’s tape works particularly well)
TOOLS
■ a video camera on a tripod
■ a ladder or step stool (to reach the top of the door frame)
■ 2 small lamps (to adjust the lighting of your video)
STEP FOUR: Now here’s the tricky part. You’re going to
run strips of tape along the wall beyond and behind the
door frame so that, from the point of view of the camera,
it looks like you’re completing the web. This is easiest
if there’s a wall running back behind the left side of the
doorway (as there is in the pictures), but if there isn’t,
you can position some furniture behind the doorway so
that you can connect the tape to the furniture.
Start by attaching a long piece of tape to the left side
of the door frame and have one person (the builder)
hold it back in the room near the wall (or furniture). The
other person (the guide) will look through the camera’s
viewfinder and tell the builder to move the tape up or
down until it looks like it goes right to the center of
the web.
Because the far end of the tape is farther away from the
camera than the rest of the tape, that end of the tape
will look too skinny to the camera. So layer a second
(and if necessary, a third) long piece of tape from the
same starting point on the door frame to a slightly
higher and/or lower end point. This “fattens” the width
of the tape on a progressive angle, but in the viewfinder,
this will make the tape appear to be the same width for
its length. Again, the guide looks through the viewfinder
and directs the builder on how to position the tape to
achieve this effect.
HERE’S WHAT YOU’RE ACTUALLY GOING TO BUILD. HERE’S WHAT THE CAMERA WILL SEE.
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HOW TO BUILD A HOVERCRAFT 6766 HOW TO BUILD A HOVERCRAFT
THE SCIENCE
STEP FIVE: In the same manner, continue to fill in the
lower left part of the spiderweb along the wall, with the
guide directing the builder to position each piece of
tape. As before, each web “strand” will actually be made
of multiple strips of tape that fatten the far ends so that
they look like the same thickness in the viewfinder.
STEP SIX: Once the web looks right in the viewfinder,
use the 2 lamps to adjust the lighting, which should be
as even as possible across the entire web. If one part
looks significantly brighter or darker than the other, that
weakens the illusion. We find it works well to have one
light shining on the web in the door frame and one light
behind shining on the web that stretches behind the
door frame.
Forced perspective is a great way to make a
toy dinosaur look like it’s attacking you or to
make you look as tall as a building. How does
it work? It’s all because a camera has only
one “eye,” and we have two.
Our two eyes give us slightly different views of the
world, which, as mentioned in the Face that Follows,
helps us judge depth. Movies in 3-D send each eye
a slightly different image, which mimics the way
our eyes work in the three-dimensional world, but
a regular camera has just a single point of view, and
everything it sees might just as well exist on the same
flat plane. The “binocular vision” of our eyes can help
discern, for example, that a tree is far behind a person,
but the two-dimensional image a camera produces can
make it look like the tree is growing right out of the
person’s head.
Most of the time, two-dimensional images work well.
Our brains use experience and other cues to judge the
relative depth and the relationship of objects to each
other, yet when objects line up in particular ways, our
brains are fooled and it can look as thought someone’s
fingertips are touching the top of the Taj Mahal.
To create the forced perspective illusion, we need
two important components. First, we need to align
separate objects in such a way that they seem to be
relating to each other. Second, we need to remove all
the clues that contradict the illusion. (For instance, if
two objects are lit differently, that can be a giveaway.)
In The Lord of the Rings, Peter Jackson put Elijah
Wood, who played the small hobbit Frodo, farther away
from the camera than Ian McKellen, who played the
normal-sized wizard Gandalf. But if that’s all he had
done, Frodo would have just appeared farther away,
so Jackson reinforced the illusion in other ways, such
as by placing an oversized mug next to Frodo and a
similar but much smaller one next to Gandalf. He also
worked hard to make it appear that the actors were
looking right at each other, even though they were
actually too far apart to do so. Equally important in
this kind of illusion are things we don’t see, such as
the floor. If we saw the big expanse of floor between
the Wood and McKellen, we would instantly realize
how far apart they were.
Want to try your own version of this trick? Here’s a
simple one. Record a video of one person pretending to
push a box while another giant person stands behind
watching. All you need are a few boxes and a video
camera. Line everything up just right, and what the
camera sees is this:
Here’s a photo of what you’re actually doing, and
the real position of each person:
Don’t show the floor. That would break the illusion.
Experiment with forced perspective and see what else
you can come up with!
For more ideas, videos, and variations, visit www.eepybird.com/experiments/spiderweb.
STEP SEVEN: Press record! You’re ready to have fun
with your web illusion and capture it on video to show
your friends. Film yourselves walking through it and
tossing things back and forth. What else can you think
of? Once you’ve got your video, see if your friends can
figure out how you did it!
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